Recently, from the viewpoint of reduction in environmental load, clean and eco-friendly liquid fuels in which the contents of sulfur and aromatic hydrocarbons are small have been demanded. From such a viewpoint, as a technique for producing a raw material hydrocarbon in order to produce a fuel oil base material that contains no sulfur or aromatic hydrocarbons and is rich in aliphatic hydrocarbons, particularly, a kerosene and light oil base material, a method using a Fischer-Tropsch synthesis reaction (hereinafter, referred to as the “FT synthesis reaction” in some cases) in which carbon monoxide gas and hydrogen gas are used as the raw material has been examined.
Moreover, a technique in which a synthesis gas whose principal component is carbon monoxide gas and hydrogen gas is produced by reforming of a gaseous hydrocarbon raw material such as natural gas, a hydrocarbon oil (hereinafter, referred to as the “FT synthetic oil” in some cases) is synthesized from the synthesis gas by the FT synthesis reaction, and further, through an upgrading step that is a step of hydrogenating and refining the FT synthetic oil to produce a variety of liquid fuel oil base materials, the kerosene and light oil base material and naphtha or wax and the like are produced is known as a GTL (Gas To Liquids) process (see the following Patent Literature 1, for example.).
As a synthesis reaction system that synthesizes the hydrocarbon oil by the FT synthesis reaction, for example, a bubble column type slurry bed FT synthesis reaction system that blows a synthesis gas into a slurry, in which a solid catalyst (hereinafter, referred to as the “FT synthesis catalyst” in some cases) particle having activity to the FT synthesis reaction is suspended in the hydrocarbon oil, to make the FT synthesis reaction is disclosed (see Patent Literature 2.).
As a bubble column type slurry bed FT synthesis reaction system, for example, an external circulating system including a reactor that accommodates a slurry to make the FT synthesis reaction, a gas feeder that blows the synthesis gas into a bottom of the reactor, an outflow pipe that evacuates from the reactor the slurry containing the hydrocarbon oil obtained by the FT synthesis reaction within the reactor, a catalyst separator that separates the slurry evacuated through the outflow pipe into the hydrocarbon oil and the FT synthesis catalyst particle, and a re-introducing pipe that re-introduces the FT synthesis catalyst particle and part of the hydrocarbon oil separated by the catalyst separator into the reactor is known.